After talking to the survivors of the recent Naxal attack in Chhattisgarh,NIA sleuths are of the opinion that the killings were carried out in the most brutal manner. According to the National Investigation Agency,the Naxals,after dragging PCC chief Nand Kumar Patel and his son Dinesh out of their cars,first shot dead Dinesh as the PCC chief continued pleading for the life of his son. According to survivors statements,the PCC chief was in tears and asked the Maoist to let go his son who was soon going to become a father. The Maoists first shot dead Dinesh and then Nand Kumar Patel,survivors told NIA. Related: Attack revenge for Salwa Judum,Green Hunt,say Maoists The NIA is trying to reconstruct the scene of the crime. On Tuesday,accompanied by technical staff of Special Protection Group,senior CRPF officials and forensic experts,the NIA team visited the site. They inspected it for nearly four hours and collected blank cartridges and other material. The vehicles which were damaged in the landmine blast triggered by the Naxals were examined by forensic experts. Related: Bastar SP suspended,Sukma SP was away The team inspected the route and nearby locations. Its not possible to mobilise such a large number of people and carry out attack on convoy without local support. We will soon announce reward for information in the case, said a senior NIA official. The officials complained that the site where the IED was planted has been repaired,which could result in difficulty in collection of evidence. The investigators are trying to locate the source of the letter which was delivered locally in Raipur,claiming responsibility for the attack. The sleuths suspect that a sympathiser from the government machinery might have helped the Naxals. An additional contingent of the Central forces has been provided to the NIA team during their movement in the region,said an official.